1. Field of the Invention
The present invention relates to a digital information encoding apparatus (an encoding apparatus based on so-called QM-Coder), a digital information decoding apparatus, a digital information encoding/decoding apparatus, a method of encoding digital information, and a method of decoding digital information, which are integrated into a semiconductor integrated circuit applied, for example, to a facsimile apparatus.
2. Description of the Prior Art
A facsimile equipment transmits binary pictures such as drawings and document texts to a remote place. The demand for a facsimile equipment to transmit the data more speedily is increasing in recent years. The transmission time has been reduced by reducing the amount of data by means of encoding.
In other words, in case of a facsimile apparatus, there are some systems for transmitting digital picture information by compressing, namely, transmitting information as an encoded data after encoding, which are now taken into the international standard. One of the system is an MH (Modified Huffman) encoding system which uses correlation between one dimensional picture elements. The second system is an MR (Modified READ) encoding system which uses correlation between two dimensional picture elements. The third system is an MMR (Modified Modified READ) encoding system which enhances the compression efficiency by eliminating redundancy of MR code.
Since it is difficult to procure a recording device which realizes a precise reproduction of the half tone picture at present, the encoding processing is carried out after pre-processing a pseudo half tone by the method called dither.
Recently, attentions are focused on the international standard group JBIG for encoding two value picture, and QM-Corder which is a highly efficient encoding system of information keeping type. The former is characterized by a high compression ratio achieved not only for picture information, but also for various kinds of information including pallet or character information. Moreover, the JBIG achieves a highly efficient compression ratio even for a pseudo half tone picture. The latter has been standardized in the standard group JPEG for color static picture encoding.
Although a digital information encoding apparatus based on the abovementioned QM-Coder is characterized by its high-speed processing, further high-speed processing is requested.
The inventors who are concerned with the present invention have carried out several investigation on the digital information encoding apparatus based on the QM-Coder, which is resulted in the following facts. The highest speed of the apparatus has been a satisfactory one. In the worst case however, namely, when the compression ration is 1, the processing speed falls to less than half of the highest speed. Accordingly, it is resulted that the total processing speed can be improved by improving the processing speed in the worst case.
It is an object of the present invention to provide a digital information encoding apparatus, a digital information decoding apparatus, a digital information encoding/decoding apparatus, a method of encoding digital information, and a method of decoding digital information, in which the total processing speed is improved, namely, the high speed processing is achieved.